As electronic and computer technology continues to evolve, communication of information among different devices, either situated near by or at a distance becomes increasingly important. It is now more desirable than ever to provide high speed communications among different chips on a circuit board, different circuit boards in a system and different systems with each other. It is also desirable to provide high speed communications in intensive data consuming systems using graphical or video information, multiple input-output channels, local area networks, etc.
Data may be transmitted between different devices in a communication system through a “data link”. The component that generates and transmits a signal through the data link may be referred to as a “transmitter”; whereas, the component that receives the signal over the data link and extracts information from the signal may be referred to as a “receiver.” Typically, data is transmitted in parallel whenever possible in order to increase bandwidth. However, due to cost, weight, interference (noise) and electrical loading considerations, parallel transmission is not feasible in many systems. In order to simplify the communications problem, data may be transmitted serially. By transmitting data serially, less hardware is required for the actual communications link between the different devices.
The transmitted serial data signal in the data link may have timing uncertainties, commonly referred to as “jitter”, as a result of what is referred to as “noise.” Noise may refer to a disturbance, especially a random and persistent disturbance, that obscures or reduces the clarity of a signal. “Jitter” may refer to the delay between the expected transition of the data signal and the actual transition. That is, “jitter” may refer to an offset of time as to when the serial data signal transitions from a high to a low state or from a low to a high state. When there is more noise in a signal there may result a greater amount of jitter thereby making it more difficult to extract the data from the signal.
Typically, in a digital communication system, data is transmitted by the transmitter without the clock signal for efficiency purposes. The clock signal may be recovered by the receiver by using a circuit commonly referred to as a clock and data recovery circuit. The clock and data recovery circuit may derive the clock signal from the received digital data.
Typically, signal generation circuits (circuits that generate a data signal) in a transmitter and clock and data recovery circuits in a receiver are designed for worst-case conditions, such as being able to handle a maximum amount of noise in the communication system. As stated above, when there is more noise in a signal, the more difficult to extract the data from the signal. This may result in designing transmitter and receiver circuits with complex configurations in order to handle the worst-case conditions. However, in many cases, the transmitted signal may contain less than the maximum amount of noise (worst-case condition), thereby unnecessarily using such complex configurations to generate the signal and/or receive and extract information from the signal. Hence, an excessive amount of power may be unnecessarily used. If the use of such unnecessary power could be reduced or if a less complex configuration could be used when the communication link is not subject to the worst-case condition, then a savings in power consumption may be made.
Therefore, there is a need in the art to reduce the power consumption in communication links (referring to the transmitters and receivers) when the communication links are not subject to the worst-case condition for noise.